1. Field of the Invention
The present invention relates to a substrate for use of an ink jet head that constitutes the ink jet head that records or prints images, such as characters and symbols, by discharging ink or some other functional liquid onto recording media, such as papers, plastics, cloths, or some other materials adoptable as print objects. The invention also relates to an ink jet head structured by use of the ink jet head substrate, an ink jet cartridge that includes an ink storing unit to store ink to be supplied to the ink jet head, as well as to an ink jet recording apparatus having the ink jet head installed thereon.
In this respect, the ink jet cartridge referred to in the specification of the invention hereof is formed detachably on mounting means, such as a carriage, arranged on the apparatus main body.
Also, the ink jet recording apparatus referred to in the specification of the invention hereof means not only the one formed integrally with an information processing apparatus, such a word processor, computer, as the output terminal thereof or formed separately therefrom, but also, means the one that includes the mode in which the ink jet recording apparatus is used for various equipment, such a copying machine having information reading devices combined therewith, a facsimile apparatus having the information transmitting and receiving functions therefor, and an apparatus that prints on textiles, among some others.
2. Related Background Art
The conventional ink jet recording apparatus uses the electrothermal converting members or piezo elements as the energy generating means that generates energy to be utilized for discharging ink. Then, it is arranged for the apparatus to enable the energy generated by this energy generating means to act upon ink or some other liquid to discharge liquid from the discharge ports. An ink jet recording apparatus of the kind is characterized in that it can record images in high precision at high speeds by discharging ink or other liquid from the discharge ports as fine liquid droplets at high speeds. The ink jet recording apparatus of the type, which uses electrothermal converting members as energy generating means that generates energy to be utilized for discharging ink, and discharges liquid by the utilization of bubbling of ink crated by the thermal energy generated by use of these electrothermal converting members, is particularly suitable for making highly precise images at higher recording, as well as suitable for making an ink jet head and the ink jet recording apparatus smaller and capable of using colors. Therefore, the ink jet recording apparatus of the type has attracted more attention in recent years. The ink jet recording apparatus that uses electrothermal converting members is disclosed in the specification of U.S. Pat. No. 4,723,129 or U.S. Pat. No. 4,740,796, for example.
FIG. 9 is a cross-sectional view which illustrates the conventional ink jet head. As shown in FIG. 9, the conventional ink jet head is provided with a plurality of discharge ports 701. Also, the electrothermal converting elements 702 that generate thermal energy utilized for discharging ink from each of the discharge ports 701 are formed on the surface of the substrate 704 per ink flow path 703 that serves as each of the liquid flow paths communicated with each of the discharge ports 701. The electrothermal converting element 702 mainly comprises a heat generating resistive element 705, the electrode wiring 706 that supplied electric power to the heat generating resistive element 705, and the insulation film 707 that protects the heat generating resistive element 705 and the electrode wiring 706. For the ink jet head of the kind, there is formed the ink jet head substrate which is provided with the substrate 704, and electrothermal converting elements 702 arranged on the substrate 704, among some others.
Also, each of the ink flow paths 703 is formed with the ceiling plate having a plurality of flow path walls 708 are formed integrally therewith, which is bonded to the substrate 704. When the substrate 704 is bonded to the ceiling plate, the electrothermal converting elements 702 and others on the substrate 704 are relatively positioned with the ceiling plate by means for image processing or the like, while being bonded to the ceiling plate. Each end portion of the ink flow paths 703 on the side opposite to the discharge ports 701 is communicated with the common liquid chamber 709. Ink supplied from the ink tank (not shown), which serves as an ink storing unit, is retained in this common liquid chamber 709.
The ink which is supplied to the common liquid chamber 709 is introduced into each of the ink flow paths 703 from the common liquid chamber 709. Then, the ink is held in each ink flow path 703 by means of the meniscus formed in the vicinity of each discharge port 701 in the flow path 703. Each of the electrothermal converting elements 702 is selectively driven, while ink is kept in each of the ink flow paths 703. Thus, by the utilization of thermal energy generated by each of the heat resistive elements 705, ink on the heat generating resistive element 705 is abruptly heated to boil. By the force of impact, ink is, then, discharged from each of the discharge ports 701.
FIG. 10 is a linear cross-sectional view which shows the portion of the substrate for use of an ink jet head used for the ink jet head illustrated in FIG. 9, which corresponds to the ink flow path 703, taken along line Xxe2x80x94X in FIG. 9. In FIG. 10, the ink jet head substrate formed by the substrate 704 and the electrothermal converting elements 702 shown in FIG. 9 corresponds to the substrate 720 for use of an ink jet head.
As shown in FIG. 10, the heat accumulation layer 722 formed by thermal oxidation film is formed on the surface of the silicon substrate 721 for the substrate 720 for use of an ink jet head. On the surface of the heat accumulation layer 722, the interlayer film 723 is formed by the SiO film that dually functions to accumulate heat or formed by SiN film or the like. On the surface of the interlayer film 723, the heat generating resistive layer 724 is locally formed. On the surface of the heat generating resistive layer 724, Al, Alxe2x80x94Si, Alxe2x80x94Cu, or some other metallic wiring 725 is formed. On the metallic wiring 725, the heat generating resistive layer 724 and the interlayer film 723, the protection film 726 are formed with SiO film, SiN film, or the like. On the surface of the protection film 726, the cavitation proof film 727 are formed to protect the protection film 726 from the chemical and physical shocks that follow the heating of the heat generating resistive layer 724. The portion of the cavitation proof film 727 other than the portion corresponding to the metal wiring 725 on the heat generating resistive layer 724 becomes the thermal activation portion 728 where heat from the heat generating resistive layer 724 acts upon ink.
For the ink jet head described in conjunction with FIG. 9 and FIG. 10, each of the heat generating resistive elements 703 is arranged for each of the ink flow paths 705. Then, recording is performed by the utilization of heat generated by the heat generating resistive elements 705. For an ink jet head of the kind, there have been increasing demands in the availability of higher images, and higher densities. As a result, various experiments have been carried out to meet such demands. For example, there has been proposed a multi-valued recording method in the specifications of Japanese Patent Application Laid-Open Nos. 62-261452 and 62-261453 in which a plurality of heat generating elements are arranged for one liquid flow path so that the heat generating elements are selectively driven to change the sizes of the liquid droplets to be discharged from the discharge ports in accordance with the multi-valued information to be recorded.
Here, however, there are restrictions given below when a plurality of heat generating elements are arranged for one ink flow path in the liquid flow direction of ink flow paths in order to implement the multi-valued recording method where the heat generating elements are arranged in the ink flow path and selectively driven.
Now, hereunder, as to the restriction on the selective driving of a plurality of heat generating elements arranged for the ink flow path, the description will be made of an example in which the first and second heat generating elements are arranged in the ink flow path in the flow path direction of the ink flow paths so as to execute the binary recording with the large dots and smaller dots by driving these two heat generating elements selectively.
At first, in this case, in order to execute the multi-valued recording more effectively, it is desirable that each of the smaller dots should be as small as possible for the higher precision, while each of the larger dots should be made as large as possible for the higher speed recording. To this end, the area of the heat generating element for use of smaller dot recording should be made smaller, while it is needed to make the area larger for the heat generating element for use of large dot recording. In this respect, the width of the heat generating element for use of the larger dot recording in the direction orthogonal to the ink flow path is automatically determined by the width of the ink flow path at first.
Then, in consideration of the condition in which the first and second heat generating elements which should be driven, it is preferable to make the driving voltage applied to the first and second heat generating elements equal. Then, there is naturally a restriction encountered that the driving voltage should be made the same as to the first and second heat generating elements.
Now, taking these two restrictions into consideration, the description will be made of the example in which the first and the second heat generating elements are arranged on the substrate in conjunction with FIG. 11 and FIG. 12.
FIG. 11 is a plan view which illustrates the example of an ink jet head having the first and second heat generating elements formed on the substrate in substantially the same sheet resistance value. In FIG. 11, the direction indicated by an arrow A is the direction of ink discharges. As shown in FIG. 11, when the first heat generating element 781 and the second heat generating element 782 are arranged serially in the ink flow path in the flow path direction of the ink flow path in that order from the discharge port side, the length L1 of the first heat generating element 781 in the flow path direction of the ink flow path and the length L2 of the second heat generating element 782 in the flow path direction of the ink flow path should be made the same in order to make the driving voltage equal. Each of the first heat generating element 781 and the second heat generating element 782 is formed to be extended in the flow path direction of the ink flow path. With the structure thus arranged, the second heat generating element 782 is away from the discharge port if the length L1 of the first heat generating element 781 and the length L2 of the second heat generating element 782 are made equal. Therefore, if a larger dot should be discharged at a higher speed, this arrangement presents a restriction. Also, the width W1 of the first heat generating element 781 for use of smaller dots in the direction orthogonal to the flow path direction of the ink flow path becomes narrower than the width W2 of the second heat generating element 782 for use of larger dots in the direction orthogonal to the liquid flow path direction of the ink flow path. Therefore, even at the maximum bubbling of the first heat generating element 781, the bubble does not reach the nozzle walls. Consequently, when bubbling and debubbling are repeated at a higher speed (4 kHz or higher, for example) in order to increase the printing speed, it becomes difficult to exhaust bubbles in each of the nozzles, which presents a restriction when the performance of the head should be enhanced.
On the other hand, FIG. 12 is a plan view which illustrates the example of an ink jet head in which the first heat generating element and the second heat generating element are structured with different heat resistive layers. In FIG. 12, the direction indicated by an arrow B is the discharge direction of ink. In this case, as shown in FIG. 12, the sheet resistance value of the first heat generating element 791 for use of the smaller dots is made larger by changing the material and film thickness. Then, by making the with W3 of the first heat generating element 791 wider, and at the same time, the length L3 of the first heat generating element 791 shorter than the length L4 of the second heat generating element 792, it is made possible to arrange the first heat generating element 791 and the second heat generating element 792 to be in the positions nearer to the discharge port. However, the manufacturing processes become complicated to change the sheet resistance values for the first heat generating element 791 and the second heat generating element 792 as described above. Then, there is encountered a problem that the costs of the ink jet head substrate and the ink jet head become higher.
Further, a structure is disclosed in the specification of Japanese Patent Application Laid-Open No. 9-239983 in which the heat generating means for use of smaller dot formation is arranged to be the one having two heat generating resistive elements electrically connected in series which are provided in parallel to the liquid flow direction, and then, the heat generating means is arranged nearer to the discharge port side in the state where the driving voltage applicable to the first and second heat generating means is almost the same.
FIG. 13 is a plan view which illustrates the structure of the ink jet head disclosed in the specification of Japanese Patent Application Laid-Open No. 9-239983.
As shown in FIG. 13, the substrate for use of an ink jet head which constitutes the ink jet head is provided with the first heat generating means 801 for use of smaller dots formed by the first heat generating resistive member 801a and the second heat generating resistive member 801b arranged for the ink flow path 808 which serves as the liquid flow path, and the second heat generating member 802 which serves as the second heat generating means. The first heat generating means 801 and heat generating resistive member 802 are arranged in series in that order from the discharge port side 807 side in the flow path direction of the ink flow path 808. The end portion of the heat generating resistive member 802 on the first heat generating means 801 side is electrically connected with the common wiring 805, and the end portion of the heat generating resistive member 802 on the side opposite to the first heat generating means 801 side is electrically connected with the individual wiring 804.
The first heat generating resistive member 801a and the second heat generating restive member 801b are arranged in parallel in the flow path direction of the ink flow path 808.
However, it is not necessarily possible even for a head of the kind to demonstrate the anticipated effect when it is driven at higher frequency to perform the multi-valued recording. In other words, there is a need for an ink jet head to arrange the heat generating resistive member and wiring per one ink flow path 808 within the pitch of the ink flow path 808. Therefore, the length L5 in the width direction of the ink flow path 808 particularly for the first heat generating resistive member 801a and the second heat generating resistive member 802b is restricted by the pitch P of the ink flow path 808. In accordance with the structure shown in FIG. 13, there is a need for the arrangement of the connecting wiring 806 in addition to the common wiring 805 and the individual wiring 803 on both sides of the first heat generating means for use of the smaller dot formation. As a result, against the flow path width, it becomes difficult to obtain a sufficient width of the heat generating means in the direction orthogonal to the ink flow path direction. Thus, the restriction is encountered when the head is driven at higher frequency to execute the multi-valued recording as described above. Now, if it is intended to secure a larger width for the heat generating means structured as described above in the direction orthogonal to the ink flow path direction against the flow path width, it becomes necessary to make the width of wiring electrode narrower, which brings about the increase of the wiring resistance. Such arrangement is not favorable at all.
With a view to solving the problems discussed above, the present invention is designed. It is an of the invention to provide a substrate for use of an ink jet head capable of discharging ink stably even in the case where the head is driven at a high frequency for the multi-valued recording, and also, capable of making the heat generating resistive member and liquid flow paths in higher densities by making the width of the first heat generating means for use of smaller dot discharges wider in the direction orthogonal to the flow path direction of the ink flow path so as to locate each of them to be more closer to the nozzle walls, at the same time, making the length of the first heat generating means essentially shorter in the flow path direction. The invention is also aimed at providing an ink jet head that uses the substrate for use of an ink jet head, as well as an ink jet cartridge and an ink jet recording apparatus.
Also, it is another object of the invention to provide a substrate for use of an ink jet head that allows the designing freedom to be increased as to the arrangement and structure of the first heat generating means for use of the smaller dot discharges, as well as the second heat generating means for use of the large dot discharges, while making it possible to reduce the costs of manufacture, and also, to provide an ink jet head, an ink jet cartridge, as well as an ink jet recording apparatus.
In order to achieve these objectives, a substrate of the present invention for use of an ink jet head that constitutes an ink jet head comprises a plurality of discharge ports for discharging liquid, a plurality of liquid flow paths communicated with the plurality of discharge ports, and first and second heat generating means arranged serially in the liquid flow paths in the flow path direction of the liquid flow paths for generating thermal energy utilized for discharge liquid in the liquid flow paths from the discharge ports, the first and second heat generating means being formed on the substrate. For this substrate, the first and second heat generating means are driven at driving frequencies of 4 kHz or more, and the first heat generating means are arranged in parallel in the direction perpendicular to the flow path direction of the liquid flow paths, at the same time, being structured with a plurality of heat generating resistive members electrically connected in series, and the second heat generating means is structured with at least one heat generating resistive member.
It is preferable to make each sheet resistance value of the heat generating resistive members forming the first heat generating means, and the sheet resistance value of the heat generating resistive member forming the second heat generating means substantially the same.
More specifically, it is preferable to enable the substrate to further comprise a common wiring layer formed on the substrate to be arranged on the substrate side of the first and second heat generating means; an insulating layer formed on the surface of the common wiring layer to be arranged as the lower layer of the first and second heat generating means; a first through hole formed on the insulating layer between the first and second heat generating means for electrically connecting the first and second heat generating means with the common wiring layer; a first individual wiring formed on the surface of the insulating layer to be electrically connected with the first heat generating means; a second individual wiring formed on the surface of the insulating layer to be electrically connected with the second heat generating means; a common wiring arranged on the side of the second heat generating means opposite to the discharge port side; and a second through hole formed on the portion of the insulating layer corresponding to the end portion of the common wiring on the second heat generating means side to electrically connect the common wiring and the common wiring layer, and then, the first heat generating means is arranged on the downstream side than the second heat generating means in the flow path direction of the liquid flow path.
Also, it is preferable to structure the first heat generating means with first and second heat generating resistive members arranged in parallel to the direction perpendicular to the flow path direction of the liquid flow path, and the first and second heat generating resistive members are electrically connected through connecting wire arranged on the discharge port side of the first and second heat generating resistive members.
Further, it is preferable to make the widths of the first and second heat generating resistive members substantially the same, and the second heat generating means is formed by one heat generating resistive member, and also, to make the length of the second heat generating means in the flow path direction of the liquid flow path substantially the same as the total length of the first and second heat generating resistive members in the flow path direction of the liquid flow path.
Further, either one of TaN, TaAl, TaSiN and HfB2 is used as the structural material of the first and second heat generating elements.
Moreover, it is preferable to make the free bubbling width of the first heat generating means larger than the maximum distance of the liquid flow path in the width direction of the liquid flow path on the arrangement portion of the first heat generating means, and also, to make the configurations and sizes of the first heat generating resistive member and the second heat generating resistive member substantially the same.
In order to achieve the objectives of the present invention, a substrate for use of an ink jet head that constitutes an ink jet head comprises a plurality of discharge ports for discharging liquid, a plurality of liquid flow paths communicated with the plurality of discharge ports, and first and second heat generating means arranged serially in the liquid flow path in the flow path direction of the liquid flow paths for generating thermal energy which is utilized for discharging liquid in the liquid flow paths from the discharge ports, the first and second heat generating means being formed on the substrate. This substrate for use of an ink jet head is provided with a common wiring layer formed on the substrate to be arranged on the substrate side of the first and second heat generating means; an insulating layer formed on the surface of the common wiring layer to be arranged as the lower layer of the first and second heat generating means; a first through hole formed on the insulating layer between the first and second heat generating means for electrically connecting the first and second heat generating means with the common wiring layer; a first individual wiring formed on the surface of the insulating layer to be electrically connected with the first heat generating means; a second individual wiring formed on the surface of the insulating layer to be electrically connected with the second heat generating means, and at the same time, the first and second heat generating means are driven at driving frequencies of 4 kHz or more, and the first heat generating means are structured with a plurality of heat generating resistive members electrically connected in series, and the second heat generating means is structured with at least one heat generating resistive member.
Also, each sheet resistance value of the heat generating resistive members forming the first heat generating means, and the sheet resistance value of the heat generating resistive member forming the second heat generating means are substantially the same.
Also, the first heat generating means is arranged on the downstream side than the second heat generating means in the flow path direction of the liquid flow path.
Also, the first heat generating means is structured with first and second heat generating resistive members arranged in parallel to the direction perpendicular to the flow path direction of the liquid flow path, and the first and second heat generating resistive members are electrically connected through connecting wire arranged on the discharge port side of the first and second heat generating resistive members.
Also, the widths of the first and second heat generating resistive members are substantially the same, and the second heat generating means is formed by one heat generating resistive member, and the length of the second heat generating means in the flow path direction of the liquid flow path is substantially the same as the total length of the first and second heat generating resistive members in the flow path direction of the liquid flow path.
Also, either one of TaN, TaAl, TaSiN and HfB2 is used as the structural material of the first and second heat generating elements.
Also, the free bubbling width of the first heat generating means is larger than the maximum distance of the liquid flow path in the width direction of the liquid flow path on the arrangement portion of the first heat generating means, and the configurations and sizes of the first heat generating resistive member and the second heat generating resistive member are substantially the same.
In accordance with the present invention described above, the first and second heat generating means are serially arranged in the flow path direction of the ink flow path, and the first heat generating means is arranged in the direction perpendicular to the flow path direction of the ink flow path. More specifically, this heat generating means is structured by the first heat generating resistive member and the second heat generating resistive member arranged in parallel in the width direction of the ink flow path. In this way, it becomes possible to make the length of the first heat generating means essentially shorter in the flow path direction. Also, the width of each of the heat generating resistive members of the first heat generating means can be made wider. As a result, the first heat generating means can be located nearer to the nozzle walls, and also, the first heat generating means and the heat generating resistive member can be arranged nearer to the discharge port along the ink flow path, hence reducing the fluid resistance toward the discharge port in order to implement the stabilization of discharges when the head should be driven at higher frequencies for the execution of a multi-valued recording. Moreover, each of the heat generating resistive members that form the first heat generating means is arranged in parallel to the direction perpendicular to the flow path direction. As a result, the connecting wiring that connects these heat generating resistive members themselves can be arranged on the discharge port side of the first heat generating means to make it possible to reduce the number of winging that should be arranged in the width direction of the ink flow path as compared with the case where each of the heat generating resistive members of the first heat generating means are arranged in parallel to the flow path direction. Therefore, the width of each heat generating resistive member can be made larger in relation to the width of the ink flow path, hence implementing the stabilization of discharges. Also, it becomes possible to attain the provision of higher density of the ink flow paths, and heat generating members as well. Furthermore, since the width of each heat generating resistive member can be made larger, it becomes possible to arrange the first and second heat generating means more closely to the discharge port side. This arrangement that makes it possible to locate the first and second generating means more closely to the discharge port side along the ink flow path indicates that the arrangement, configuration, and size of each heat generating member can be changed within a range that does not lower its discharge characteristics. In other words, it becomes possible to enhance the freedom in designing the heat generating resistive members for the attainment of a multi-valued recording. In this manner, it becomes possible to increase the designing freedom in consideration of the balance between each of the heat generating means up to the maximum of such increased freedom as to the arrangement and structure of the first and second heat generating means. Consequently, in addition to the stabilized liquid discharges for a multi-valued recording, the heat generating resistive members and liquid flow paths can be arranged in higher density.
Also, as the structural material of the first and second heat generating means, the one having almost the same sheet resistance value is used unlike the conventional means where a plurality of heat generating resistive members are adopted with different sheet values. As a result, it becomes possible to suppress the manufacturing costs of the substrate for use of an ink jet head, the ink jet head, and the ink jet cartridge.
Further, the structure is adopted so that the first and second heat generating means are arranged serially on the common wiring layer with the first through between the first and second heat generating means. Therefore, it becomes possible to locate the first and second heat generating means more closely to the discharge ports within the limited width of each of the liquid flow paths. In this way, the aforesaid effects can be demonstrated. In addition, the number of wires arranged in the width direction of liquid flow path can be made smaller. To that extent, then, the width of each of the heat generating resistive members can be made wider in relation to the width of each liquid flow path, hence implementing the stabilized discharges, at the same time, attaining the provision of higher density for the liquid flow paths and the heat generating resistive members as well.
Further, an ink jet head of the present invention comprises a substrate for use of an ink jet head described above, and a ceiling plate bonded to the surface of the substrate for use of an ink jet head on the first and second heat generating means side so as to arrange the liquid flow paths on the surface of the substrate for use of an ink jet head on the first and second heat generating means side.
Further, an ink jet cartridge of the present invention comprises an ink jet head described above, and a liquid storing unit to store liquid to be supplied to the ink jet head.
Further, an ink jet recording apparatus of the present invention comprises an ink jet cartridge described above, and a recording medium carrier device for carrying a recording medium to receive liquid discharged from the ink jet head of the ink jet cartridge.
In accordance with each of the above-described inventions, it is possible to discharge liquid stably for recording even when a multi-valued recording is required, and also, it becomes possible to obtain an ink jet head, an ink jet cartridge, and an ink jet recording apparatus, with which to execute recording of highly precise images in higher resolution.
In this respect, the phrase xe2x80x9cthe free bubbling width of heat generating meansxe2x80x9d referred to in the specification of the invention hereof indicates the maximum development of a bubble which is bubbled by heat generating means in the state where there is essentially no fluid resistive component on the circumference thereof.